Livetrak L-12 Question about USB Input

[Pioterman]

Hello, I have a Zoom Livetrak L-12 mixer. I plugged it into my PC as an Audio Interface (switch on the rear panel of the mixer). I have installed the correct drivers for Windows 10. The operating system recognizes the hardware correctly. When I select USB channel 1-2 on L-12 (the backlight comes on), the mixer plays music from the computer correctly. When I turn off USB 1-2 and turn on USB 3-4 (the backlight comes on), the signal from the computer does not reach the mixer. The analog inputs of channel 11-12 (i.e. USB 3-4) work properly. Could there be any damage to the digital USB 3-4 input? How can I check this? I reinstalled the drivers and checked the situation on several different computers. It's the same everywhere.